Preprints  

A novel technique for the uranium-lead dating of geologically young carbonates is described and tested. The technique expands our ability to date geological events such as fault movements and past climate records.

The timing and duration of fluid activity within a gold deposit enables a greater understanding of how the deposit evolved and thus help future mineral exploration. This research uses high resolution dating methods to unravel the overprinting fluid activity at the Martabe gold field in Sumatra. Methods outline in this report can be applied to deposits globally.

We carried out thermal annealing experiments between 500 and 1000 °C to determine the closure temperature of radiation-damage annealing in zircon (ZrSiO₄). Our results show that the different Raman bands of zircon respond differently to annealing. The repair is highest for the external rotation Raman band near 356.6 cm⁻¹. The closure temperature estimates range from 250 to 370 °C for different bands. The differences in closure temperatures offer the prospect of multi-T zircon Raman dating.

This paper shows that the current practice of filtering discordant U-Pb data based on the relative difference between the ²⁰⁶Pb / ²³⁸U and ²⁰⁷Pb / ²⁰⁶Pb ages is just one of several possible approaches to the problem, and demonstrably not the best one. An alternative approach is to define discordance in terms of isotopic composition, as a logratio distance between the measurement and the concordia line. Application to real data indicates that this reduces the positive bias of filtered age spectra.

This paper demonstrates how to model OSL and radiocarbon ages in a Bayesian framework, using a dedicated software tool called BayLum. We show the effect of stratigraphic constraints, of modelling the covariance of ages when the same equipment is used for a series of OSL samples, and of including independent ages on a chronological inference. The improvement in chronological resolution is significant.

Luminescence dating requires irradiating the sample in the laboratory. Some concerns have been published recently about the reliability of the calibration procedure. Here we have addressed these concerns. We found that the interplay between geometrical parameters such as grain size and aliquot size impact on the calibration more than previously thought. The results allow us recommending improved calibration procedure to enhance the reliability of the calibration value.

To explore the U-Pb geochronometer in fluorite, the spatial distribution of uranium and other substituted elements in natural crystals is investigated using induced fission-track and synchrotron radiation X-ray fluorescence mapping. LA-ICP-MS U-Pb dating on four crystals, that preserved micrometer-scale variations in U concentrations, yield identical ages within analytical uncertainty. Our results show that fluorite U-Pb geochronology has potential for dating distinct crystal growth stages.

We generated a synthetic dataset applying published kinetic models and distinct annealing kinetics for the apatite fission-track and (U-Th)/He methods using a predetermined thermal history. We then tested how well the true thermal history could be recovered under different data interpretation schemes and geologic constraint assumptions using the Bayesian QTQt software. Our results demonstrate that multikinetic data increase time-temperature resolution and can constrain complex thermal histories.

Here we present the foundation dataset for “TephraNZ”, a formal, comprehensive, open access, reference dataset of glass-shard compositions for New Zealand tephras. We geochemically characterise 45 eruptive episodes ranging from Kaharoa (c. 636 cal. yrs BP) to the Hikuroa Pumice member (c. 2.0 Ma) from six or more caldera sources, most from the central Taupō Volcanic Zone.

Past climate conditions have had an influence on coastal landscape dynamics in the Siberian Arctic. Coastal deposits can help to reconstruct variability and predict future changes. In this study, we show that the age of old beach shorelines can be reliably obtained by dating driftwood. This is surprising, as the wood travels long distances through large rivers. With this knowledge, the timing of past coastal change can be identified and precisely dated in marine deposits containing driftwood.

Artificial intelligence techniques are capable of detecting fission tracks automatically in minerals. The here presented AI-Track-tive software can be used to automatically determine fission track densities for apatite fission track dating studies. Apatite fission track dating is mainly applied to tectonic studies studying exhumation rates in orogens. Now, time-consuming manual track counting is replaced by deep neural networks capable of automatically finding the large majority of the tracks.

We introduce a new model of confined fission-track revelation, which simulates the etching process and accounts for variable along-track etching rates. This complete characterization explains many observations, including community difficulty in obtaining consistent track length measurements. It also provides a quantitative basis for optimizing etching procedures, and ultimately deriving more robust and reproducible fission-track ages and thermal histories.

High-resolution geochronology is one of the key factors to predict explosive volcanic eruptions. To build up high-resolution geochronology, we report 21 new high-precision 40Ar/39Ar ages for a ~3.3 million years old volcanic history on Milos, Greece. In combination with geochemical information and eruption volumes from the volcanoes of Milos, the long-lived volcanic history could provide important clues for the prediction of volcanic eruptions.

We present the results of a series of experiments that constrain the temperature sensitivity of fission tracks in monazite over geological time. It was concluded that over a heating duration of ten million years the estimated closure temperature is < 50 °C and perhaps not much above ambient surface temperatures. Monazite fission track thermochronology has the potential to understand the thermal history of the Earth's upper crust (< 1–2 km) and constrain the timing of geological processes.

This paper describes GeoChronR, an R package that streamlines the process of quantifying age uncertainties, propagating uncertainties through several common analyses, and visualizing the results. In addition to describing the structure and underlying theory of the package, we present five real-world use cases that illustrate common workflows in GeoChronR. GeoChronR is built on the Linked PaleoData framework, is open and extensible, and we welcome feedback and contributions from the community.

We characterize three natural carbonate samples with elevated uranium/lead (U/Pb) ratios to demonstrate techniques for characterizing carbonates for U/Pb dating. With the rapidly accelerating application of laser ablation analyses, there is a great need for well-characterized standards. The three samples we describe have good potential as standards. In addition to U/Pb data, we present strontium (Sr) isotope analyses to demonstrate that these could be dual standards for U/Pb and Sr isotopes.

Potassium-based geochronology, including the ⁴⁰Ar/³⁹Ar and K-Ar methods, provides critical constraints on the timing and duration of many events and processes in earth history. These methods assume that a key parameter, the fraction of potassium with a mass of 40, does not vary in some relevant materials. Some recent work has identified some variability in these materials. This work examines the effects of this variability on calculated K-Ar and ⁴⁰Ar/³⁹Ar ages.

We compare two published U-Pb and ⁴⁰Ar/³⁹Ar geochronologic datasets used to produce different eruption rate models for the Deccan Traps LIP. We conclude that differences in eruption rates arise not from inaccuracy of dates, but instead from the way the data were presented. Applying the same statistical approach to each dataset, the resulting models agree well, but the higher precision U-Pb dataset generates a more nuanced eruption model that is untestable with the lower precision ⁴⁰Ar/³⁹Ar data.

A new methodology for the micron-scale uranium-lead dating of carbonate minerals is proposed. It is based on the extraction of ages directly from the pixels images (< 1 mm²) obtained by laser ablation coupled to a mass spectrometer. The ages are calculated with a robust linear regression through the pixel values, which is an efficient and simple approach to that can be easily applied to mineral dating.